Conversion valve



Patented Jan. 28, 1941 UNITED STATES PATENT OFFICE CONVERSION VALVEApplication February 19, 1940, Serial No. 319,611

11 Claims.

This invention relates to a conversion valve employed to obtain balancedremote control for a trailer with air suspended power brakes, saidbrakes being regulated by a tractor equipped r vacuum suspended powersystem. On the other hand a conversion valve of this type is adaptablefor trailer brake control of the air suspended type, even though thetractor itself has no vacuum power brakes, but has a control valve foroperatill ing said conversion valve on the trailer. As described in mycopending application, Serial No. 310,904, vacuum power brake units areof two distinct types; atmosphere and vacuum suspended, both unitsutilizing vacuum taken off the intake it manifold of an internalcombustion engine.

When the air suspended power brake unit is inoperative atmosphericpressure is equal on both sides of the brake operating piston. Bypermitting vacuum from the intake manifold to comm municate with one endof the power cylinder, the air on that side of the brake operatingpiston is withdrawn and air pressure on the other side of the brakepiston causes motion thereof, whereby the brakes are applied.

at In the vacuum suspended brake system a double line of vacuum isapplied to both sides of a brake piston for maintaining brake release.By actuating a, control valve air is admitted to one side of the pistonforcing the same to move longitudigp nally, whereby mechanical brakingpower is obtained. in the present application the power brake system forthe tractor is of the latter vacuum suspended type, while the powerbrake system for the trailer is of the former air suspended as p Theconversion valve hereinafter more particularly described, is utilizedwhereby the trailer brakes may be remotely actuated at the same time as,or sooner than, the tractor brakes are .m actuated.

Conversion valves of this type usually consist of chambers bounded on atleast one side by an elastic diaphragm, said chambers containing air andvacuum respectively. It is desirable for ob- M taining a balance in avalve of this type that there be a definite relationship, for instance,between the air pressures in the chambers, and between the degrees ofvacuum in the other chambers.

to A valve operating stem disposed within a conversion valve of thistype is designed for movement whenever there is a lack of balance ofpressures between all the chambers. It is the motion of this stem whichregulates the operation of the its vacuum power brakes;

I-Ieretofore conversion valves of this type have not operated aseffectively as desired because no effective means have been employedwhereby the balancin chamber of said valve is not affected by vacuumchanges in the system. 6

It is desirable that the vacuum in said balancing chamber be maintainedbecause of the control it "has over the valve stem actuating diaphragmhereinafter described, which in turn controls operation of the trailerbrakes. By 10 maintaining this vacuum prompt and more completelyresponsive braking action of the trailer brakes is affected.

In all conversion valves of this type the balancing vacuum chamber is incommunication with the vacuum source. As this source is drawn upon toactuate the air suspended brake chambers the vacuum power available mustdrop, due to the air entering into the vacuum source from said chambers.The net result of a vacuum drop in the aforementioned balancing chamberis that the valve action is not completely responsive but lags. Thisinvention provides a mechanism whereby this drop in the vacuum isprevented at the moment that a drop of vacuum 00 ours in the vacuumsource.

It is the object herein to provide a conversion "valve wherein themaximum vacuum in the balancing chamber is constantly maintained wherebya greatly improved valve action is accomplished or obtained.

It is the object hereof to provide means in a conversion valve of thistype wherebythe vacuum within the balancing chamber may be temporarilycut off from communication with the vacuum source at the moment thatsaid source begins to drop.

It is the further object hereof to provide a. novel method employed in aconversion valve of this type whereby a very quick action is obtained.

It is the further object hereof to provide in a. conversion valve abalancing vacuum chamber of such interior volumetric contentas to reduceair compression therein by operation of the diaphragm which ordinarilywould compress what air remains in said chamber. By reducing thiscompression to a minimum valve action is also increased preventing lagor delay which hereto fore has been characteristic of this type ofvalve.

This invention relates to the various arrange- 5 ments of parts andcombinations thereof hereinafter described by way of example inconnection with the appended drawing of which:

Figure 1 is a sectional elevational view of the conversion valve.

Figure 2 is a side elevational view of the conversion valve assemblywith the brake power chambers.

It is expressly understood that the invention is not limited by saiddrawing, but is intended to cover other adaptations within the scope ofthe invention teaching various applications of the principles embodiedherein.

Referring to the drawing the upper vacuum balancing chamber i of theconversion valve defined by the cover portion 2 suitably boltedcircumferentially to the valve housing 3 at points 6, communicates withthe vacuum tank or other vacuum source by means of a by-pass 5 withinsaid housing, said by-pass in turn communicating with the vacuum inletconnection 3 from said vacuum supply.

Transversely disposed across the open top of housing 3 secured by cover2 is an elastic diaphragm or disc i which resiliently defines vacuumbalancing chamber 5. Diaphragm i also defines chamber 8 which is furtherbounded at its bottom by the web portion 9 integral with the valvehousing, access being provided thereto through opening iii.

A second diaphragm or disc ii is likewise secured within the valvehousing in spaced relation to the aforementioned web member to define anair chamber it open to the atmosphere through openings l3. A fourthchamber id communicating with vacuum inlet connection 6 is providedbelow and adjacent diaphragm ii, said chamber being in directcommunication through outlets is": and conduits it to the power chambersill of the trailer brakes.

For brake release, chamber it directly communicates with the atmospherethrough openings it in the housing, said openings communicating with afilter it retained within the lower portion of valve housing 8 betweenscreen 69 and filter plate assembly 253, said filter being retained bymeans of the cover member 2i and a suitable bolt In normal brake releaseposition the seat assembly 23 resiliently positioned upon coil spring 26is unseated with respect to the laterally disposed annular valve seat25, whereby air is free to pass upwardly through guide member 26 whichretains and journals the hollow valve disc member 2i. It will be notedthat in brake release position disc 27 is seated upon the annularopening 28 which communicates with the vacuum supply through inletopening 6, effectively closing off said vacuum supply from chamber l4.

In brake release, balancing chamber 9 is provided with a maximum vacuum;likewise chambar 8 which communicates with the control line 29 throughopening l8. Line 29 is connected with a control valve which is manuallyor otherwise operated Within the tractor whereby vacuum is transmittedto chamber 8. It is through this control line also that air or reducedvacuum may be allowed to enter said chamber thereby varying the degreeof vacuum therein.

In release position it will be seen that there is I a balance of vacuumbetween chambers I and 8,

tlon therethrough. Diaphragms l and II are fixedly secured to stem 30for reciprocation therewith. diaphragm ii being resiliently positionedwith respect to corresponding chambers 62 and id by coiled springs 32and 33 respectively.

Operation To apply the trailer brakes it is necessary to temporarilyupset the balance obtained in. the conversion valve during brake releaseby admitting air or reduced vacuum through control line 29 into chamber8. Due to the variation in degree of vacuum between chambers l and 8diaphragm i is caused to instantly rise or flex within chan'iber i.Diaphragm ii and stem 36 likewise move in the same direction, stem 38carrying therewith loosely mounted guide member 26 by means of collarportion 39 and unseating valv disc 27!.

Vacuum supply within the annular opening 28 is permitted to enterchamber H3 contemporaneously. Independent seat assembly 23 is permittedto rise under the force of its resilient spring support 2 whereby saidassembly effectively registers with seat 25 closing oii further airsupply to chamber 5 3. Vacuum power within chamber M then becomesavailable through openings l5 and conduits E6 to the power chambers ll,whereby the trailer brakes are applied.

Application of the brakes brings about a temporary lack of balancewithin the conversion valve. as vacuum is built up in chamber 66, airpressure in chamber 52 forces diaphragm ii downward, aided by theresiliency of compressed spring Stem 3E9 consequently floats downwardwith valve disc 2? and its support 26 riding upon collar of said stem.It will be noted that due to the resiliency of the diaphragm and springsthat valve disc 2'? does not seat itself over annular opening nor isdisc assembly 23 unseated from seat seat 25 being resiliently supportedby spring 25.

At this point a new balance is obtained within the conversion valve withthe brakes applied, the vacuum in chamber i l being again equal in dereeto the vacuum in chamber 2.

When it is desired to release the trailer brakes the control line 29 isregulated by control valve whereby vacuum is again supplied to chamber 8and the existing balance is again temporarily disturbed until a newbalance can be obtained between diaphragms i and i i The vacuum built upin chamber 8 causes further downward movement of diaphragm 8 and alsodiaphragm ii and stem 39 connected thereto. Guide member 25 riding incollar 36' of stem 36, causes valve disc 2? to seat over annular opening26, closing off further vacuum power from chamber i5. Valve seatassembly 23 is unseated from seat 25 by the downward movement of stem 3twhereby air through inlets I8 is allowed to enter chamber M asheretofore described.

With air in chamber i6 and in chamber I2 and with equal degrees ofvacuum in chambers i and 8 balance is again obtained between diaphragmsl and ii.

Whenever only partial braking is required a mixture of air and vacuum ora limited degree of vacuum is permitted to communicate through line 28with chamber 8, by partial operation of the control valve.

Thus" diaphragm 1 moves upward with less force applied, due to a smallerdegree of vacuum difierential between chambers I and 8. With vacuumpermitted to build up in chamber II, in the manner heretofore described,disc 21 is seated again, as soon as the pressure differential betweenchambers I2 and I l is equal to the vacuum dlflerential between chambersI and 8. However it will be noted that stem 30 descends only far enoughto allow disc 21 to seat but not far enough to unseat disc assembly 23.Partial braking is thus accomplished, because vacuum supply is again cutoil from chamber I4 so that said chamber has therein a mixture or airand vacuum, 1. e., a reduced degree of vacuum sealed in chamber I4 incommunication with the power brake chambers. Consequently at this pointa balance is obtained within the conversion valve after the applicationof the partial braking.

In conversion valves of this type vacuum balancing chamber I iscontinuously in communication with the vacuum supply. Whenever thissupply is drawn upon to operate the trailer brakes with power chambersof the air suspended type it is obvious that there will be a, drop ofvacuum in the vacuum supply due to the air entering into the vacuumsource from said brake chambers which in turn would be communicated tobalancing chamber I.

This vacuum drop prevents a prompt and quick upward movement ofdiaphragm I at the moment, the air or reduced vacuum is allowed to enterchamber 8 through control line 29.

This invention includes a method and means whereby diaphragm 'I is morereadily responsive for actuating the trailer brakes in the mannerhereinbefore described, said diaphragm being integral with the mechanismwhich controls vacuum power to said brakes.

Cover member 2 is provided upon its lower surface with an annular recess34 which is adjacent to and in communication with by-pass channel 5whereby in brake release vacuum is free to communicate with chamber I.

It will be noted also that the annular flange M forming a portion of theinterior surface of cover member 2 and defining the interior wall ofannular recess 34 is adjacent the outer portion of diaphragm I; but inrelease position, as shown in Figure 1, is provided with a clearance oropening 36 therebetween for communication between Icy-pass 5, recess 34and chamber I.

At the instant however that air is admitted to chamber 8 through valvecontrolled line 25 and diaphragm I starts to rise, opening 36 is closedby the upper surface of said diaphragm effectively sealing chamber Ifrom further communication with the vacuum source.

Thus the vacuum within balancing chamber I is maintained at its maximumand a prompt, non-lagging, completely and instantly responsive valveaction is obtained for braking application.

It will be noted that there always will be some air in chamber I becausea perfect vacuum is never effected therein. This air is compressed uponupward movement of diaphragm 'I and therefore must offer resistance tothat movement. The invention herein contemplates providing chamber I ofsufiicient volumetric content that this compressive force will have noappreciable effect upon upward movement of diaphragm I.

Tests have shown that by taking this compressive force intoconsideration, and providing a large enough interior for chamber I, thatthis compression is reduced to a minimum, and valve action is greatlyimproved and made more completely responsive.

The conversion valve is designed to speed up,

for instance, trailer braking, by making the source or vacuum power foroperating the brakes in close proximity to the power brake chambers.

The conversion valve housing I Is provided with separate outlets II towhich are connected conduits I8 joining the power brake chambers I1.This arrangement provides a more direct communication between theconversion valve and trailer brakes.

Having described my invention reference should now be had to the claimswhich follow for determining the scope hereof.

I claim:

1. In a conversion valve, 0. by-pass therein for conducting vacuum to avacuum chamber into which a diaphragm actuated vacuum regulating valvestem is movable, a cover member defining said chamber and means integralwith said cover member with which said movable diaphragm cooperates Iorintermittently sealing the same from said by-pass.

2. In a conversion valve for air suspended vacuum power brakes, meansfor conducting vacuum to a vacuum chamber, said chamber being bounded bya movable valve stem actuating diaphragm, a housing confining saidchamber, said housing being provided with an annular recessed portioncommunicating with said means, a diaphragm disposed within said housingadjacent said recessed portion and normally in spaced relation thereto,said diaphragm being movable within said chamber to intermittently sealthe same from the vacuum conducting means.

3. In a conversion valve, a housing, a cover member defining a chamber,a by-pass in said housing for conducting vacuum to said chamber, meansdefining an inlet opening from the by-pass to said chamber, and areciprocable diaphragm forming a part of said chamber to which issecured a vacuum controlling valve stem, said diaphragm cooperativelyregistering intermittently with said inlet defining means, for sealingsaid chamber from said by-pass.

4. In a conversion valve, a by-pass in the housing therefor, a housingcover member defining a vacuum chamber communicating with said bypass,said chamber being bounded by an axially and reciprocably moveable valveactuating diaphragm, and means integral with said cover member withwhich said diaphragm co-operatively registers for intermittently sealingsaid chamber from the by-pass.

5. In a conversion valve, means for conducting vacuum to a chamber intowhich a diaphragm actuated vacuum regulating valve stem is moveable, acover member defining said chamber, means integral with said covermember with which said moveable diaphragm co-operates for intermittentlysealing the same for said vacuum conducting means, the interiorvolumetric con tent of said cover member being such that reduc tion ofthat volumetric content by said diaphragm, with consequent vacuumreduction therein, will not retard the free upward move ment of saiddiaphragm.

6. In a conversion valve, a housing therefor, a cover member and amoveable means defining a chamber, means for conducting vacuum to saidchamber, means integral with said cover member with which said moveablemeans co-operates for intermittently sealing said chamber from thevacuum conducting means.

'7. In a conversion valve, a housing therefor, a cover member and amoveable means defining a chamber, means for conducting vacuum to saidthat reduction of that volumetric content by said moveable means, withconsequent vacuum reduction therein, will not retard the free upwardmovement of said moveable means.

8. In a conversion valve, a housing therefor provided with an openingfor conducting vacuum to a chamber, a cover member and a moveable meansdefining said chamber, means integral with said cover member with whichsaid moveable means co-operates to intermittently seal said chamber fromthe vacuum conducting means.

9. In a conversion valve, a housing therefor, a cover member defining achamber, a vacuum controlled valve actuating diaphragm disposed Withinsaid housing adjacent a recessed portion therein and normally in spacedrelation thereto, forming a part of said chamber, and meanscommunicating with said recessed portion to conduct vacuum to saidchamber, said diaphragm being moveable therein to intermittently sealthe same from the vacuum conducting means.

10. In a conversion valve, a by-pass therein for conducting vacuum to avacuum chamber into which a diaphragm actuated vacuum regulating valvestem is moveable, a cover member defining said chamber, and meansintegral with said cover member with which said moveable diaphragmcooperates, for intermittently sealing the same from said icy-pass, theinterior volumetric content of said cover member being such thatreduction of that volumetric content by said diaphragm, with aconsequent vacuum reduction therein, will not retard the free upwardmovement of said diaphragm.

11. In a conversion valve, a by-pass in the housing thereof, a housingcover member defining a vacuum chamber communicating with said by-pass,said chamber being bounded by an axially and reclprocably moveable valveactuating diaphragm, and means integral with said cover member withwhich said diaphragm cooperatively registers for intermittently sealingsaid chamher from the icy-pass, the interior volumetric content of saidcover member being such that reduction of that volumetric content bysaid diaphragm, with consequent vacuum reduction therein, will notretard the free upward movement of said diaphragm.

GORDON R. ELLIOTT.

